GSK cancer vaccine disappoints in melanoma trial

LONDON (Reuters) - An experimental cancer vaccine from GlaxoSmithKline failed to help melanoma patients in a closely watched late-stage clinical trial, dealing a blow to the high-risk, high-reward project.

Britain's biggest drugmaker said on Thursday that it would continue with the Phase III trial of its MAGE-A3 therapeutic vaccine to see if it benefited a subset of patients with a particular genetic signature.

The trial has two joint targets, known as co-primary endpoints, looking at both the broad population and a patient subset, so it is possible the treatment will yet prove effective for a small number of people with the deadly skin cancer.

It is also being tested in lung cancer.

Unlike traditional preventative vaccines, the MAGE-A3 treatment is designed for people with established disease, helping their immune systems to prevent the return of disease after surgery.

Other companies, including Bristol-Myers Squibb, Roche and Merck & Co, have had some recent notable successes in clinical trials of innovative drugs to boost the immune system, but GSK is still pushing the scientific boundaries with its MAGE-A3 vaccine.

DIFFICULT AREA

Cancer vaccines have proved difficult to develop over the years. A different vaccine for lung cancer from Germany's Merck KGaA also failed in a clinical test last December.

GSK's vaccine was developed for use in patients with tumors that express the cancer-related MAGE-A3 gene, which occurs in about 65 percent of Stage III melanomas.

It failed to extend disease-free survival significantly when compared with placebo in this population in the Phase III study.

The second endpoint of the trial is to discover whether disease-free survival is improved in a subset of MAGE-A3-positive patients. Results from this analysis are expected in 2015.

GSK added that no safety issues had emerged in the trial.

"We remain committed to identifying a patient sub-population who may benefit from this investigational treatment," said Vincent Brichard, head of immunotherapeutics at GSK Vaccines.

A spokesman said it was not yet possible to say what proportion of patients might fall into this subset.

GSK is also continuing to study MAGE-A3 in another Phase III study against non-small cell lung cancer. The first data from this trial are expected in the first half of 2014.

Alistair Campbell, of Berenberg Bank, described the chances of a success in lung cancer as "slim."

"This asset was widely regarded as a 'wild card' by the market. While there had been some hope that this approach might work, the result is not a surprise," he said in a research note.

Although the news on melanoma was disappointing, Campbell noted that 2013 had still been a strong year for GSK research, with new drug approvals in HIV, cancer and respiratory disease.

GSK is now waiting to hear if its latest lung drug, Anoro, will be approved. A U.S. Food and Drug Administration advisory panel is set to assess the medicine on Sept. 10.